An ultrasonic transducer array built in an ultrasonic probe is known as a vibrator array having a plurality of vibrators arranged in an array manner on a base plate. The ultrasonic transducer array includes a backing material as a base plate, piezoelectric elements as vibrators, an electrode, and an acoustic impedance matching layer.
In manufacturing of the ultrasonic transducer array, a wafer of, for example, PZT (lead zirconium titanate) which is a material of the piezoelectric elements is bonded to the backing material by an adhesive. After the electrode, the acoustic impedance matching layer and the like are stacked on the wafer, grooves are made on the wafer by dicing process at predetermined intervals to reach a part of the backing material from the acoustic impedance matching layer. The wafer is divided into a plurality of piezoelectric elements with the grooves. Filling materials are filled in the grooves and the ultrasonic transducer array is completed.
In the ultrasonic transducer array, each piezoelectric element vibrates at high speed in the thickness direction to generate ultrasounds. When it vibrates in the thickness direction, vibrations in the width direction also occur. There is a problem that such width directional vibrations unstabilize the vibration action of each piezoelectric element in the thickness direction and thus negatively influence acoustic characteristics of the ultrasonic transducer array.
In order to solve the above problem, Japanese Patent Laid-Open Publication No. 2001-046368 discloses a manufacturing method of an ultrasonic probe which has piezoelectric elements formed in an almost trapezoid to gradually increase the width toward the backing material to restrain the unnecessary vibrations of the piezoelectric elements in width direction.
However, in the method disclosed in Japanese Patent Laid-Open Publication No. 2001-046368, the piezoelectric elements are thermally deformed by friction heat on the dicing process. In order to solve the problem, polishing powder such as alumina powder is mixed in the backing material, therefore cost increases.